calendar_schedule_unavailable· reason_code· applies to event_envelope, state_resolutionAn RSVP or occurrence expansion was attempted while the deterministic Calendar schedule winner is encrypted_unresolved rather than available. See zh/models/calendar-event.md. This is an authoring-side and projection-side code, never a server admission gate: deciding readability requires the Calendar subtree plaintext, so gating admission on it would fork the accepted set between e2ee and plaintext Realms.